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Help selecting an I-beam


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Hello All,  first time on the Forum. I am hoping someone can help me select the correct size and material for an I-beam for a personal project.

Briefly,  I have installed heavy industrial shelving( like you see at Home Depot)in an airplane hangar.  I have suspended or cantilevered them instead of having them rest on the ground. This is an unconventional installation but I wanted to preserve my work area. The back portion of the vertical components rest solidly on a horizontal beam.  The front portion is unsupported from below however it is suspended from the lower flange of the ceiling I-beam.  The front portion has a 1/2-13 rod extended through it’s length that I thought I would attach to an I-beam resting on the upper flange of the buildings large ceiling I-beam(see yellow line in attached photo). I am hoping that someone can help me select the correct size and material for the I-beams.  The span of each section is twenty feet.  A section would hold no more than 2,000 lbs spread evenly over the shelving. I am certain I have left out important details but I will insert some photos of the installation thus far.  Again, the yellow line is where I would like to place the I-beam on the upper flange of the ceiling I -beam. I am considering aluminum and a material called Dynaform. Any assistance you can give me is greatly appreciated.  Mike









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Since I am hearing nothing but crickets here, maybe a little more information will coax someone to respond.  Again, I would like to place the I-beams in question on the upper flanges of the existing structural I-beams.  The would simply rest on the upper flanges and attach to the upper horizontal portion of the front part of the racks with all thread rod.  Please see yellow line in one of the attached images.  The racks will attach to the I-beams by using all thread rod that runs the length of the forward leg.  You can see these rods extending upward from each forward leg in this photo:



I am thinking of using this material for the I-beams:



ANY input would be appreciated.  Thanks!

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Mike, I am pretty sure this would violate the building code. As you add loading to the roof without permission.
but if you insist, this the mechanical equations.


you get the maximum M, use stress = M c/ I and compare it with the steel I-beam strength/limit

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Hi there!  


This is definitely NOT advisable!

The roof is calculated out for the wind loading and the snow loading (as appropriate) with a margin of safety....it is NOT designed to be loaded in addition to this...not without appropriate calculation and checks!

If you add static loading to the roof, it significantly lowers the design load of the structure from "environmental Factors"...basically, if it snows, it could collapse, if it is windy it could collapse and if there is a sandstorm (as appropriate) - Insurance would not pay out in a failure of this nature (not to mention the risk to those within).

To give an example...In Southern UK, a high risk structure I calculated recently has a design snow load (although it hasn't really snowed here for 30 years...) of 2kN/m^2 ...it doesn't really sound a lot...but looking at the size of your roof...that's a huge loading!

Contextually, 2kN is only 200kg per m^2...which is carried on each beam for the span...from your picture it looks like the beam supports about 4 m^2 for every metre length ....add to that, every time you drill the beam (assuming you're not using rod-lugs) you add a stress concentrator in the hole itself. The safety factor is added to the maximum load for the structure...but you have already significantly increased the static load of the structure, so your roof safety factors MUST be shot to pieces!

It could well be fine, but get a structural engineer to look at this and recalculate...it will cover all eventualities, your insurance will be happy and you will have the comfort blanket of the calculations to help you sleep soundly at night!

Good luck 




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Hi Bruce,

Thank you so much for responding!   As I am sure you can tell, I am not an engineer so any input you can give me is greatly appreciated. 

If you don’t mind, I would like to describe to you, in a non-quantitative way, more detail regarding my arrangement with these shelves. I would like you to understand the arrangement better and I would like to get a feel for what risks I have created and if these problem areas can be mitigated.

If you don’t mind I would like to describe for you the arrangement in two steps.  The first being the shelf structure that is in the plane of the outer wall.  The second will be the plane perpendicular to that, I.e., the shelves that extend toward the interior, away from the wall.

First, in the plane of the wall:

In Drawing 1 and 2 as well as the photos one you can see that in the plane of the structure’s supporting I-beam columns the shelve’s horizontal tubular beam rests on the I-beam flange at either end of it’s 20‘ span.  I removed the shorter 3/4” bolt and replaced it with a longer, similar grade 3/4” bolt.  By the way, NO new holes were drilled in any of the building’s structural components at any stage. The vertical tubular steel shelf columns are attached with 6” x 6” x 3/8” steel “L” brackets as well as a 1/4” “U-shape Bracket from above(see photo). They are attached with 1/2-13 bolts. This arrangement created a very rigid framework in the plane of the building’s I-beam columns.  The bottom of the shelf columns rest on one of the structure’s horizontal support beams. 

Shelf tubular beam resting on and bolted to the buildings I-beam flange:




Attachment of vertical shelf components:



Attachment of shelf horizontal beams.  Note wide flange and 1/2”-13 bolts.



Lower shelf vertical tubular component resting on structure’s horizontal support beam showing L-bracket for adjusting and maintaining it in a plumb position:


This is a column from the shelf that is not in the plane of the supporting beams but it illustrates a complete view of how the shelf columns are attached:


Drawing of the very rigid grid work that was created in the plane of the building’s vertical I-beam supporting columns and horizontal supporting beam:


As you can see thus far, to my untrained eye, a very rigid structure has been created in the plane of the structure’s supporting beams. Again, to my untrained eye, any forces placed on the shelf beams would be supported by the building’s vertical columns and the building’s horizontal support beam and I would not expect it to adversely affect the building.

Bruce, I am very interested in your thoughts thus far.  

I believe the real problem will come in the next section when we discuss what happens when we discuss the forces outside the plane of the Building’s vertical columns.


Thanks again for thoughts on this project.  I really do appreciate your help!





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Hopefully you will have an opportunity and the inclination to respond to my last post; I am looking forward to your input. I thought I would just move forward until then.  

The shelves obviously don’t just stay in the plane of the buildings I-beam columns.  If they did they certainly would be very shallow shelves.  They do extend forty inches  away from the wall via three braced vertical components:



The outer most part of these vertical components rest on the lower flange of the roof I-beam; like the similar component in the plane of the building’s vertical I-beam:


With the addition of the shelf beams the shelves have become a very rigid structure, almost like a monocoque airplane fuselage. 

It seems to me that the point that is concerning is that any static loads placed on the shelves will be transmitted to the ceiling beam.  Is this correct? If this is so, would a strut placed between the building’s vertical I-beam and the roof I-beam help to mitigate the static load?  See drawing 4:



Thanks in advance for your input,



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